1. Field of the Invention
The present invention relates to an electrochemical device; and, more specifically, to an electrochemical device encompassing electrochemical capacitors such as electric double layer capacitors and batteries such as lithium ion secondary batteries.
2. Related Background of the Invention
Electrochemical capacitors such as electric double layer capacitors and batteries such as lithium ion secondary batteries have been expected to become power supplies or backup power supplies for portable devices (small-size electronic devices) and the like, and auxiliary power supplies for electric or hybrid cars, for example, since they are electrochemical devices which can easily reduce their size (thickness) and weight.
Among such electrochemical devices, cells having a form referred to as coin type have been known in general as those of thin type. However, such a coin type cell has a structure in which end parts of upper and lower lids made of a metal constituting a shell are crimped together so as to seal the inside, whereby the shell is required to have a sufficient strength and is needed to be thicker. Therefore, it has been difficult for the coin type electrochemical device to be made smaller (thinner). As the upper and lower lids constituting the shell, those also functioning as external output terminals have been in use in general.
On the other hand, Japanese Patent Application Laid-Open No. 2002-313679, for example, discloses an electric double layer capacitor in which a member (collector metal) constituting the shell also functions as a collector (and an external output terminal), and an end part of the collector metal is bonded with a heat-bonding part without crimping, so as to yield a sealed structure, thereby reducing its size (thickness).